The purpose of this project is to identify and describe by means of accurate physical measurement and rigorous quantitative analysis the characteristic patterns of change in cranio-facial morphology which are associated with specific types of therapeutic intervention by orthodontists and maxillo-facial surgeons for the correction of maxillary disphasia. The study attempts to examine, as much as feasible, a range of currently acceptable types of treatments and to assess both immediate and long range effects. It includes the examination of control groups of untreated subjects with malocclusions and osseous dysplasias matching those of the treatment groups in an attempt to obtain comparable data on the natural course of developmental changes in similar subjects in the absence of therapeutic intervention. Specialized computer-assisted methods incorporating well-developed error detection algorithms have been developed and are being progressively refined for use in measuring skull x-ray films and photographs of dental study casts. These methods are used to acquire numerical data concerning short and long range changes in (a) the conformation of the skull and jaws, (b) the positional relationships between the teeth, and (c) thickness and contour of the pharyngeal and facial soft tissues. These numerical data are used to construct a computer-readable relational data base. A complementary rapidly accessible data base consisting of images of the same x-ray films and study cast photographs from which the numerical data are obtained is also being constructed. The ability to cycle rapidly between the pictorial and the numerical data facilitates interpretation of the findings, especially in cases where real outlying numerical values exist for key variables. The accumulated data are used for computer-conducted hypothesis-testing experiments whose general aims are to test the goodness of current theory in explaining the observed effects of treatment and to aid in the development of better theories and better methods of treatment.